In presently utilized excavators, e.g. hydraulic excavators, the effort is made to provide the user with the greatest possible number of possibilities of use with work equipment, so that the booms of the excavators are designed in such a way that front work attachments can be exchanged at the boom. Thus, excavator shovels can be exchanged for two clam shell grabs, for hydraulic grabs, hydraulic hammers, vacuum lifters and the like, to list only a few possibilities.
A device for the coupling when receiving and changing a front work attachment is known, e.g. from WO 83/03629. In the latter, the connection of excavator booms and work equipment is effected by means of coupling plates which are arranged at the work equipment and excavator boom. The coupling plate arranged at the work equipment is provided with various catch recesses constructed as projections; catch elements of various shapes, which are connected with the coupling plate of the excavator boom, engage in the catch recesses in order to receive the work equipment. At least a portion of these catch elements is constructed so as to be movable around an axis and can be positioned by the driver from the driver's seat in order to be inserted into the corresponding catch projections which are provided with corresponding bore holes for the positive-locking engagement of the catch elements.
The coupling process is further reinforced in that as soon as an opening, which is provided at the coupling plate of the excavator boom, engages around a locking bar projection, which is arranged at the coupling plate of the work equipment, a movable locking bar, which is arranged at the coupling plate of the excavator boom, is pressed into the locking bar projection via a hydraulic or mechanical device until all catch elements are securely locked into the corresponding catch projections. The excavator boom and the work equipment are now securely connected with one another.
Such a coupling device has several grave disadvantages. On the one hand, e.g. if the bore holes of the catch projections become stopped up with rubble or earth, the catch elements can only be pressed into the catch projections with a great expenditure of force, which is transmitted to the catch elements by means of the interaction of the locking bar and locking bar projection. On the other hand, a force which is generated by the load acts on the locking bar element and locking bar projection when the work equipment is received by the excavator boom. Both of these cases result in quick wear and inoperativeness of the locking elements. These individual parts must therefore be exchanged frequently, which is very time-consuming and cost-intensive.
It is the object of the invention in particular to provide a solution by means of which the consequences of appearances of wear at the locking elements for the coupling for receiving and changing a front work attachment for an excavator boom can be sharply reduced, wherein a quick coupling of the work equipment to the excavator boom is simultaneously ensured.